In general, once cartilage tissue that forms the joints of vertebrates is damaged, the cartilage tissue is very difficult to normally regenerate in vivo. When the cartilage tissue of the joints is damaged, a patient feels severe pain and the patient's daily activities may be limited. Further, when chronic, degenerative arthritis or the like can lead to fatal complications, and the normal life or professional activity of the patient is hindered, thereby greatly affecting the daily lives of modern people.
This cartilage damage occurs at a high frequency due to osteoarthritis causing traumatic defects or the gradual destruction of articular cartilage tissue. Thus, studies on a method of treating osteoarthritis have been conducted, for example, chondroplasty, osteochondral transplantation, autologous chondrocyte transplantation and the like have been performed, but in the case of surgery of a relatively young patient under 60 years old, there is a problem in terms of the lifespan of artificial joints.
Furthermore, although a local injection therapy of directly injecting steroid agents or hyaluronic acid into the joints has been widely used, while these anti-inflammatory drugs have an effect of alleviating symptoms, weakened cartilage and systemic side effects may be caused and damaged cartilage cannot be generated, and thus the local injection therapy using anti-inflammatory drugs cannot be a fundamental treatment. Therefore, when drugs capable of inducing regeneration of cartilage in the osteoarthritic region are applied to the local injection therapy, the effect of the treatment may be enhanced.
Recently, kartogenin has been reported as a drug that can induce chondrogenic differentiation of adult mesenchymal stem cells, and it was determined from animal experiments with mice that kartogenin triggers the activity of mesenchymal stem cells in cartilage to generate chondrocytes, thereby recovering damaged cartilage. However, since a kartogenin compound has a very low molecular weight, is water-insoluble and exhibits hydrophobic properties, there is a limit in application thereof as a drug.
Moreover, in terms of a method of administration of a drug for treating osteoarthritis, a method of intra-articular injection is a treatment method showing the highest expected effect due to directly injecting drugs into damaged joints. However, since drugs in a liquid state injected into the joints are quickly dispersed and the retention time thereof in the joints is too short, it is necessary to increase the concentration of drugs or the number of doses, but this may rather lead to systemic side effects.
Therefore, for local intra-articular injection for the effective treatment of osteoarthritis, studies on a composite that not only improves the biocompatibility of hydrophobic drugs such as kartogenin and also enables continuous drug release have been carried out (Korean Patent Publication No. 10-2014-0090481), but it remains inadequate.